Intonation problem up the neck

[Mark Miller]

My mandolin has developed an intonation problem or imbalance. When the open strings are in tune, once I get up to the 7th fret or so they run sharp. It wasn’t this way always, but it definitely is now. I first noticed it when playing outside on a hot and humid day and thought maybe it was just the temperature and humidity change making it wonky. But after being back inside for a couple of days, the problem is less severe but still there. Is this something I can address myself or do I need to take my baby to the doctor?

[colorado_al]

It sounds like you need to adjust the location of the bridge. Loosen the strings and move the bridge towards the tailpiece a few mm. Then tune up at least the outside strings and check the intonation. Play the 12th fret harmonic and then fret the 12th and play it. They should be the same. If still sharp, move the bridge further towards the tailpiece. If flat, move the bridge slightly back towards the neck. Repeat until intonation is correct.
You might find that you have to angle the bridge slightly to get all the strings to intonate properly. That is common, and not a problem

[pops1]

If the weather changes and your top swells your intonation will also change so you can do one of two things. Check string height, and if it raised, lower it and see if your intonation returns, or move the bridge to regain it.

[Mark Miller]

Thank you guys. I’ll give it a shot. Yet another example of the knowledge and generosity of folks on this site!

[Br1ck]

You need Rob Meldrum's free eBook on setup. Lots of useful info. Just E mail him for it.

[Rob Meldrum]

Br1ck is right. Email me at rob.meldrum@gmail.com and put Mandolin Setup in the subject line.

If your strings are higher than optimal they will exacerbate any intonation issues. Ditto if the nut slots are not filed correctly.

Good luck!

Rob

[Drew Egerton]

You might also have enough fret wear to be causing issues, how worn out are they?

[Mark Miller]

Thanks Rob--an email is on its way to you. Drew--I just had the lower frets replaced and the upper ones evened out about a year ago, so all set there. It was really nicely set up then too. I'm hoping that with the help of the advice here and Rob's book I can make some minor changes and straighten this out. It's not as bad as it was the other day--when, as I said, I had just moved to a hot and humid day from an air conditioned house--but there is still some slight edging towards sharp starting at about the 5th or 7th fret.

[Tom Wright]

Arched tops will typically rise higher with increasing humidity. Cello players sometimes have summer bridges to switch out to instead of winter bridges.

If your top swelled, the strings will be a bit higher, as pops1 said. This will make them play sharp and you can compensate by either lowering the bridge or moving it. Likely it is only a string height issue.

[Mark Miller]

Thanks Tom, that helps me understand the mechanics (or physics?) of what is likely to have happened. The strings do seem a bit higher--in fact I had noticed that but not made much of it--I thought it might be my imagination. And it explains why that happened to my mandolin and not my (flattop) guitar. I'll try lowering the bridge a tiny bit and see what happens. The glory of an adjustable bridge: I guess it makes the mandolin more finicky than a guitar but more easily adjustable.